Apparatus for the electrical separation of coal



July 6, 1937. K. c. APPLEYARD ET AL 2,086,060

APPARATUS FOR THE ELECTRICAL SEPARATION OF COAL Fild Aug. 10, 1936Patented July 6, 1937 UNITED v attests orrlcs APPARATUS FOR THEELECTRICAL SEPARATION OF COAL Kenelm Charles Appleyard, Birtley, andStanley Dallas Pollitt, Newcastle-on-Tyne, England, as-

signors to The Birtle ley, England y Company Limited, Birt- 2 Claims.

This invention relates to the separation of coal by electricaldiscrimination, and especially to apparatus for separation according toour British Patent No. 421,401, but it is not limited to such apparatus,especially, for instance, as regards voltages and amplification.

The object of the invention is to provide an improved or modifiedapparatus, especialy from the aspect of reducing the valve requirementsin a number of machines working together, or in a machine of what mightbe called a multi-pass type, that is, where a number of sets ofdiscriminating brushes or the like come into question.

The invention in brief consists in apparatus 5 for the sorting of coalby electrical discrimination, in which the different conductivity orlike efiects produced in an electric circuit by the passage of the coalbeing sorted, which coal forms part of that circuit, are used to controla single electric discharge tube, which is rendered available to a,plurality of machines or coal separating paths, for instance,constituted by means of a conveyor band passing the coal through gapsbetween resilient electrical contacts, which electrical discharge tubeacts to determine the disposition of the sorted materials.

The invention also consists in apparatus according to the precedingparagraph in which the electric discharge tube is rendered available toa plurality of discriminating devices by means of two or morecommutators or rotary switches rotated at a suificiently high speed, oneof these commutators being in connection with the anode of the dischargetube, and a series of relay circults, dealing with the control of thedischarge arrangements, or with the maintenance of a suitable timeinterval by holding-on circuits, or by other desired devices, andanother commutator being associated with the grid of the valve, and

the discriminating devices. 7

The invention also consists in apparatus according to either of thepreceding two paragraphs, in which direct current is employed inconnection with the devices associated with the anode commutator, andalternating current is employed in connection with the cathode side ofthe electric discharge device.

The invention also consists in apparatus for the sorting of coal,substantially as herein described.

One way of calrying the invention into effect by way of example will nowbe described with reference to the accompanying drawing, whichrepresents diagrammatically a scheme for the electrical separation ofcoal from associated impurities. V V 7 Referring to the drawing, a gridcontrolled mercury vapour filled discharge tube I having an anode 2, agrid 3 and a cathode l is used to 5 deal with a conveyor band l5constituting five coal separating channels it to M in each of which apiece of. coal is shown, each of which has what may be termeddiscriminating fingers in sets at right angles suitably electricallyconnected, as 0 shown conveniently in Figure 1 of the drawingaccompanying the complete specification of British Patent No. 421,491,especially taken in conjunction with Figures 7 and 8 of that pat ent.

The discriminating devices numbered 5 to 9 1 5 and the valve I, with itsassociated circuits, are co-related by means of two five-partcommutators, IE3 and H respectively, each commutator consisting of fiveelements l2 to It and H to ill corresponding in number to the fivecleaning 20 channels, and each element being divided into four sectionsmutually opposed at right angles, the four sections of each elementbeing electri cally connected.

The commutators ill and II have co-operating brushes 22 to 26 and 21 to3! respectively which are electrically connected in each commutator, Inthe case of the commutator H, a connection is made from the brushes tothe anode 2 of the valve I, and in the case of the other commutator Ill, a connection is made from the brushes to the grid 3 of the valve 9.For convenience, the commutators will therefore be referred torespectively as the anode and grid commutators.

Each of the above mentioned conductive sec- 35 tions of the commutatorelements is of such a peripheral length that when the five elements ofthe commutators are fixed on the shaft 32, they may be so adjustedrelative to one another that their corresponding brushes will makecontact 40 with only one section at a time, and in a complete revolutionof the shaft 32 each brush will have made four contacts on thecorresponding element of the commutator orin all twenty separatecontacts will have been made by the set 45 of brushes. The peripherallength of the contact also bears such a relation to the diameter of thecommutator that the brushes in passing from one segment to another passover a space of insulation. 50

The commutators are mounted on the hollow shaft 32 which is capable ofbeing rotated at high speed, and on this shaft two sets of slip rings 33and 34 are mounted, each set comprising five rings of conductivematerial, with co-operat- 55 ing brushes, the rings being insulated fromthe shaft and connected by leads passing through the inside of the shaftto their respective commutators IE and ii. The rings which are thusjoined to the grid commutator have their respective brushes connected toone side of the discriminating fingers 5 to 9, the other side of thesefingers being connected to earth.

The brushes of the set of slip rings 34 which are associated with theanode commutator H are electrically connected with a series of relayswitches 35, 35, 31, 38 and 39. These relays when actuated energizesolenoids M3, ll, 42, 43 and 4 3 which in turn open and close doors 45,46, 41, 48 and 59 for the passage of one of the separated constituents,for example, stone (compare the hinged flaps shown in positions 54 and44a in British specification No. 421,401) They may also control knownhold-on circuits by way of auxiliary switches 6%, til, '62, E3 and 64mechanically connected to the aforesaid relay switches, the function ofthe auxiliary switches being to see chat the circuit is closed fora'suitable time, and remains closed for a longer period than would bepermitted solely by the valve action, having regard to the high speed ofrotation of the commutator shaft 32, which speed may be for examplebetween 700 and 2,000 revolutions per minute.

The power for the door operating solenoids 40 to M is convenientlyderived from a source of alternating current 59 of substantial amount,for instance, at a high voltage, say 440 volts, and 50 cyclesperiodicity. The power for the relays is provided by a source of directcurrent, such as the battery Si or a motor generator, of voltagesuitable for the work, say between 100 and 800 volts. When a battery isused, a number of cells are tapped elf and connected to earth, whichreally means that the earth connection is at some potential above earth,and this may be varied.

The relay coils 53 to El, which may have resistance-capacity circuits 52connected in parallel as shown in the drawing, are connected to thepositive end of the battery 5i through door limit switches 65, 56, 51%,69 at the end of the relay coils remote from the slip rings, and arethereby always at a positive potential. From the other end of the relaycoils 53, 5d, 55, 56 and 5'! connections are taken to the slip rings 34and thence via the commutator l l to the anode 2 of the valve I. Fromthis same end of each relay coil a connection is taken to one side ofthe corresponding auxiliary switch, of the group 653 to fi l, and fromthe other side of this auxiliary switch a connection is taken to thenegative end of the battery 5! through a rheostat 58. Should one of the"elay switches, say 35, momentarily close due to the passage of currentin the valve I, the corresponding auxiliary switch (it will retain acircuit through the solenoid lfi until the door &5 opens fully, soopening the limit switch 65 associated with it. In place of limitswitches which open and break the circuit when. the doors reach thefully open position switches may be mounted inside the doors in such aposition that the pieces of material passing through the doors will openthe said switches and break the circuit. The ca hode l of the valve l isheated by a step-down transformer winding 59 from the source ofalternating current 59.

In operation, the coal to be classified passing along any of thedistributing channels is tested by a rapid series of impulses, due tothe combined action of the high speed commutators l0 and II and thevalve l, and in accordance with the result the filament.

of the test, it is caused to pass to the appropriate destination, thatis, either through the trap doors or not through the trap doors 55 etc.The duration of contact of the brushes on any one segment of thecommutator is of such small magnitude that should the valve pass currentduring the contacting period of this segment and the condition of thegrid circuit have changed before another contact is made on thiscommutator so that current does not now pass, then such a single impulseis insuflicient to energize the relay to such an extent as to make itsassociated auxiliary switch make the hold-on circuit, and the door willtherefore remain closed. The distance through which the relay parts mustpass as a result of the passage of current in the valve itself beforemaking contact on its auxiliary switch may be adjusted. Because of thevery small inertia of the valve and the comparatively immense inertia ofthe relay parts, we are enabled to integrate the resistance of any pieceof material as it passes through the brushes. Thus, if during thepassage of a piece of material through the brushes the valve isconnected thereto twenty times by the revolving commutators and passescurrent on fifteen occasions, the relay auxiliary switch can be soadjusted as to make contact and operate the trap door. By means of thisintegrator we are therefore enabled to separate hard coal from softbecause of the greater conductivity of the hard. This has been extremelydifilcult up till now, because of the fact that all soft coal containsstreaks and laminations of hard which on making contact with the brushesoperated the relay and opened the trap door.

General The grid circuit of the valve I may be connected through aresistance 10 to the negative side of the battery. It is thereforealways at negative potential, but at a potential lower than that of Theanode is always at a constant potential but due to the revolvingcommutators this potential is obtained via the different relay coils inturn, while the grid has applied to it the potentials of the variousdiscriminating fingers in turn, which potential is dependent upon thenature of the piece of material at that instant between the saidcontacting fingers. The commutators being mechanically mounted on oneshaft ensure that the anode current will always flow through the relaycoil corresponding to the contacting finger which is at that instantsupplying the grid potential. Because direct current is used there cannever be any phase lag between the anode and grid, due, for example, tovarying capacities of the material. The holding-on circuits give timefor the doors to be opened, notwithstanding the fact that perhaps manyimpulses will have followed in the valve before in fact opening takesplace.

We have found that by using a single selector valve circuit for aplurality of discriminating paths, in addition to the economy in valves,wiring and other matters, obtained in this way, in comparison with asingle valve operating a single unit, there appear to be otheradvantageous efiects, especially, for instance, when the coal is evenquite wet, because matters can be so adjusted that the valve willdistinguish between the constituents of Wet coal, and permit the wetcoal to pass, While rejecting the wet stone.

We claim:

1. Apparatus for sorting coal comprising a single grid controlledelectric discharge tube, a set of flexible contacts for testing thecoal, a multiple rotary switch adapted to complete a circuitsuccessively with the flexible contacts arranged to contact pieces ofcoal fed along a plurality of separate parallel paths and a source ofdirect current in an electrical circuit which is arranged to influencethe potential of the grid of the discharge tube, a set of relays, asecond and corre- 10 sponding multiple rotary switch and a source ofdirect current in the anode circuit of the discharge tube and pathselecting devices operated by a, source of alternating current andinfluenced by the current in the anode circuit of the'discharge tube todetermine the path of each piece of coal. V

2. Apparatus for sorting coal electrically as claimed in claim 1including a conveyor band along which the coal is passed through gapsbetween resilient electrical contacts.

KENELM CHARLES APPLEYARD. STANLEY DALLAS POLLITT.

7 CERTIFICATE OF CORRECTIONL'I. Patent No. 2,086,060. y 6; 957

1mm CHARLES APPLEYAR ET AL.

It is hereby 'certified that the above numbered patent was erroneouslyissued to "The Birtlej Compeny Limitedtas assignee of the entireinterest in said invention whereas said patent shonl-d have been issuedto the inventors, Kenelm Charles Appleyard and StanleyDallas Pollitt,and the Birtley Company Limited, 'said company being assignee ofone-third interest only in said invention, as shown by the records ofassigniuents in-this office; and that the said Letters Patent should beread with this correction therein that the same may conform to therecord of, the casein the Patent Office.

Signed and sealed this 12th day of QetoberfA. D. 1957.

Henry' Van Arsdale. (Seal) Acting Commissioner of Patents.

